Merge tag 'rust-6.2' of https://github.com/Rust-for-Linux/linux

Pull rust updates from Miguel Ojeda:
 "The first set of changes after the merge, the major ones being:

   - String and formatting: new types 'CString', 'CStr', 'BStr' and
     'Formatter'; new macros 'c_str!', 'b_str!' and 'fmt!'.

   - Errors: the rest of the error codes from 'errno-base.h', as well as
     some 'From' trait implementations for the 'Error' type.

   - Printing: the rest of the 'pr_*!' levels and the continuation one
     'pr_cont!', as well as a new sample.

   - 'alloc' crate: new constructors 'try_with_capacity()' and
     'try_with_capacity_in()' for 'RawVec' and 'Vec'.

   - Procedural macros: new macros '#[vtable]' and 'concat_idents!', as
     well as better ergonomics for 'module!' users.

   - Asserting: new macros 'static_assert!', 'build_error!' and
     'build_assert!', as well as a new crate 'build_error' to support
     them.

   - Vocabulary types: new types 'Opaque' and 'Either'.

   - Debugging: new macro 'dbg!'"

* tag 'rust-6.2' of https://github.com/Rust-for-Linux/linux: (28 commits)
  rust: types: add `Opaque` type
  rust: types: add `Either` type
  rust: build_assert: add `build_{error,assert}!` macros
  rust: add `build_error` crate
  rust: static_assert: add `static_assert!` macro
  rust: std_vendor: add `dbg!` macro based on `std`'s one
  rust: str: add `fmt!` macro
  rust: str: add `CString` type
  rust: str: add `Formatter` type
  rust: str: add `c_str!` macro
  rust: str: add `CStr` unit tests
  rust: str: implement several traits for `CStr`
  rust: str: add `CStr` type
  rust: str: add `b_str!` macro
  rust: str: add `BStr` type
  rust: alloc: add `Vec::try_with_capacity{,_in}()` constructors
  rust: alloc: add `RawVec::try_with_capacity_in()` constructor
  rust: prelude: add `error::code::*` constant items
  rust: error: add `From` implementations for `Error`
  rust: error: add codes from `errno-base.h`
  ...

2 files changed, 121 insertions, 1 deletions

diff --git a/rust/alloc/raw_vec.rs b/rust/alloc/raw_vec.rs
index daf5f2da7168..eb77db5def55 100644
--- a/rust/alloc/raw_vec.rs
+++ b/rust/alloc/raw_vec.rs
@@ -20,11 +20,11 @@ use crate::collections::TryReserveErrorKind::*;
 #[cfg(test)]
 mod tests;
 
-#[cfg(not(no_global_oom_handling))]
 enum AllocInit {
     /// The contents of the new memory are uninitialized.
     Uninitialized,
     /// The new memory is guaranteed to be zeroed.
+    #[allow(dead_code)]
     Zeroed,
 }
 
@@ -133,6 +133,13 @@ impl<T, A: Allocator> RawVec<T, A> {
         Self::allocate_in(capacity, AllocInit::Uninitialized, alloc)
     }
 
+    /// Like `try_with_capacity`, but parameterized over the choice of
+    /// allocator for the returned `RawVec`.
+    #[inline]
+    pub fn try_with_capacity_in(capacity: usize, alloc: A) -> Result<Self, TryReserveError> {
+        Self::try_allocate_in(capacity, AllocInit::Uninitialized, alloc)
+    }
+
     /// Like `with_capacity_zeroed`, but parameterized over the choice
     /// of allocator for the returned `RawVec`.
     #[cfg(not(no_global_oom_handling))]
@@ -203,6 +210,30 @@ impl<T, A: Allocator> RawVec<T, A> {
         }
     }
 
+    fn try_allocate_in(capacity: usize, init: AllocInit, alloc: A) -> Result<Self, TryReserveError> {
+        // Don't allocate here because `Drop` will not deallocate when `capacity` is 0.
+        if mem::size_of::<T>() == 0 || capacity == 0 {
+            return Ok(Self::new_in(alloc));
+        }
+
+        let layout = Layout::array::<T>(capacity).map_err(|_| CapacityOverflow)?;
+        alloc_guard(layout.size())?;
+        let result = match init {
+            AllocInit::Uninitialized => alloc.allocate(layout),
+            AllocInit::Zeroed => alloc.allocate_zeroed(layout),
+        };
+        let ptr = result.map_err(|_| AllocError { layout, non_exhaustive: () })?;
+
+        // Allocators currently return a `NonNull<[u8]>` whose length
+        // matches the size requested. If that ever changes, the capacity
+        // here should change to `ptr.len() / mem::size_of::<T>()`.
+        Ok(Self {
+            ptr: unsafe { Unique::new_unchecked(ptr.cast().as_ptr()) },
+            cap: capacity,
+            alloc,
+        })
+    }
+
     /// Reconstitutes a `RawVec` from a pointer, capacity, and allocator.
     ///
     /// # Safety
diff --git a/rust/alloc/vec/mod.rs b/rust/alloc/vec/mod.rs
index 540787804cc2..8ac6c1e3b2a8 100644
--- a/rust/alloc/vec/mod.rs
+++ b/rust/alloc/vec/mod.rs
@@ -472,6 +472,48 @@ impl<T> Vec<T> {
         Self::with_capacity_in(capacity, Global)
     }
 
+    /// Tries to construct a new, empty `Vec<T>` with the specified capacity.
+    ///
+    /// The vector will be able to hold exactly `capacity` elements without
+    /// reallocating. If `capacity` is 0, the vector will not allocate.
+    ///
+    /// It is important to note that although the returned vector has the
+    /// *capacity* specified, the vector will have a zero *length*. For an
+    /// explanation of the difference between length and capacity, see
+    /// *[Capacity and reallocation]*.
+    ///
+    /// [Capacity and reallocation]: #capacity-and-reallocation
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let mut vec = Vec::try_with_capacity(10).unwrap();
+    ///
+    /// // The vector contains no items, even though it has capacity for more
+    /// assert_eq!(vec.len(), 0);
+    /// assert_eq!(vec.capacity(), 10);
+    ///
+    /// // These are all done without reallocating...
+    /// for i in 0..10 {
+    ///     vec.push(i);
+    /// }
+    /// assert_eq!(vec.len(), 10);
+    /// assert_eq!(vec.capacity(), 10);
+    ///
+    /// // ...but this may make the vector reallocate
+    /// vec.push(11);
+    /// assert_eq!(vec.len(), 11);
+    /// assert!(vec.capacity() >= 11);
+    ///
+    /// let mut result = Vec::try_with_capacity(usize::MAX);
+    /// assert!(result.is_err());
+    /// ```
+    #[inline]
+    #[stable(feature = "kernel", since = "1.0.0")]
+    pub fn try_with_capacity(capacity: usize) -> Result<Self, TryReserveError> {
+        Self::try_with_capacity_in(capacity, Global)
+    }
+
     /// Creates a `Vec<T>` directly from the raw components of another vector.
     ///
     /// # Safety
@@ -617,6 +659,53 @@ impl<T, A: Allocator> Vec<T, A> {
         Vec { buf: RawVec::with_capacity_in(capacity, alloc), len: 0 }
     }
 
+    /// Tries to construct a new, empty `Vec<T, A>` with the specified capacity
+    /// with the provided allocator.
+    ///
+    /// The vector will be able to hold exactly `capacity` elements without
+    /// reallocating. If `capacity` is 0, the vector will not allocate.
+    ///
+    /// It is important to note that although the returned vector has the
+    /// *capacity* specified, the vector will have a zero *length*. For an
+    /// explanation of the difference between length and capacity, see
+    /// *[Capacity and reallocation]*.
+    ///
+    /// [Capacity and reallocation]: #capacity-and-reallocation
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(allocator_api)]
+    ///
+    /// use std::alloc::System;
+    ///
+    /// let mut vec = Vec::try_with_capacity_in(10, System).unwrap();
+    ///
+    /// // The vector contains no items, even though it has capacity for more
+    /// assert_eq!(vec.len(), 0);
+    /// assert_eq!(vec.capacity(), 10);
+    ///
+    /// // These are all done without reallocating...
+    /// for i in 0..10 {
+    ///     vec.push(i);
+    /// }
+    /// assert_eq!(vec.len(), 10);
+    /// assert_eq!(vec.capacity(), 10);
+    ///
+    /// // ...but this may make the vector reallocate
+    /// vec.push(11);
+    /// assert_eq!(vec.len(), 11);
+    /// assert!(vec.capacity() >= 11);
+    ///
+    /// let mut result = Vec::try_with_capacity_in(usize::MAX, System);
+    /// assert!(result.is_err());
+    /// ```
+    #[inline]
+    #[stable(feature = "kernel", since = "1.0.0")]
+    pub fn try_with_capacity_in(capacity: usize, alloc: A) -> Result<Self, TryReserveError> {
+        Ok(Vec { buf: RawVec::try_with_capacity_in(capacity, alloc)?, len: 0 })
+    }
+
     /// Creates a `Vec<T, A>` directly from the raw components of another vector.
     ///
     /// # Safety